1. Field of the Application
The present invention relates to a plasma processing apparatus, and more particularly, to an inductively-coupled-plasma (ICP) type plasma processing apparatus.
2. Description of Related Art
Plasma processing apparatuses using high frequency (HF) to generate plasma can be classified into capacitively-coupled-plasma (CCP) type plasma processing apparatuses capable of generating capacitively-coupled plasma and inductively-coupled-plasma type (ICP) plasma processing apparatuses capable of generating inductively-coupled plasma.
It can simply say that a radiofrequency voltage is applied to two parallel electrodes and a high frequency electric field generated between the two electrodes is used to generate plasma in CCP type plasma processing apparatuses.
In the CCP type plasma processing apparatuses, there are problems causing the plasma potential to become higher due to a high voltage applied to the plasma. Since charged particles (e.g., ions) of the plasma impinge on the substrate with a high energy, the damage induced to the film which is formed on the substrate may increase and deteriorate the film quality.
On the other hand, in ICP type plasma processing apparatuses, an induction electric field generated by applying a radiofrequency current to flow to an antenna is used to generate plasma. Basically, compared with the CCP plasma processing apparatuses, the ICP plasma processing apparatuses have the advantage of being capable to lower the plasma potential.
Taking the ICP plasma processing apparatus as an example, in International Publication No. WO 2009/142016 (paragraphs [0024] to [0026], FIG. 1), a flat-board-like antenna is mounted on an opening of a vacuum container through an insulating frame. A high frequency power supply is supplied to the flat-board-like antenna so that a high frequency current can flow from one end to the other end of the antenna, and thereby plasma is generated due to the induced electric field. It has been described in WO 2009/142016 that the plasma is used to perform a plasma treatment to the substrate in the plasma processing apparatus.